So signal straight from the variable reluctance sensor is -5,5V? How is it converted to TTL? Detect the crossover? Should I assume the speedo (electrical one) signal is the same, and it is converted to TTL at the speedo itself?

I was apparently wrong... (I said no. The input logic apparently does just that.)

Also, thanks for that link. I did not realize how particular grounds are in a car with FI. Which leads to ground loops: I've always wondered if it would be wise to put a diode in series with the grounds to the devices you want to not be confused by a noisy ground. Or am I just trying to complicate something already complicated?

ZVOLV, back to the crank sensor picture where you have a sawtooth wave,
is this after being conditioned? And what about this one?
was it read at the same place as the previous one? I ask because I would think the fuel system would want to know where the reference point (the missing tooth) is. Oh wait, when converting to square wave the "nothing" region is still there. Duh!

But, now that it is converted to square wave, is the signal then pulse width or pulse frequency modulation?

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You are going to have to open up an old ECM and analyze the circuit for the ignition input. In fact, I am not sure whether you will need to open up the ignition box (EZK) or the Jetronic box. I would be seriously surprised is the input logic on either controller is as sophisticated as the construction of that MAXIM package.

I never did hear back from the guy about my diagrams. It's okay. He has to screenshot that ish when his boss isn't around and send it to me. Isn't there an online link for the wiring diagrams on these cars floating around somewhere???

ZVOLV, kinda interesting because the output is a sawtooth wave; I would expect it to look more like a sinusoidal thingie because analog. Learning something new every day!

swedefiend, I thought, on the ignition side, the power stage would get the VR signal and convert it to a nice square tooth signal before sending it out. And the same would go for the speedo (thinking here a 2.4 Volvo 740): VR signal goes to the speedo which then sends it to the LH ECU. If it does that, it must be doing some sensual massaging to the signal before letting it go, right?

The EZ116K box conditions the VR CPS signal using an analog comparator setup as a zero crossing detector (Horwitz&Hill has a rough example). The processor in the EZK decodes the 60-2 tooth pattern and generates a Tach signal that goes to the LH2.4 ECU, and a Spark signal to the ignition module.

While the Maxim VR conditioner chip seems really nice on paper, it has proven troublesome in the MicroSquirt ECU when trying to decode a Volvo 60-2 VR signal at higher RPM. The stock EZK circuits are much more reliable. For those who want to dig deeper, here's a post by Bruce Bowling and others about the MicroSquirt 60-2 problems: http://www.msextra.com/forums/viewto...art=40#p271449 Search this forum for Volvo 60-2 MicroSquirt specific suggestions.

I think jbperf.com still sells Maxim VR conditioner boards (or you could PM FreeEMSFred and see if he has any left of his design).

The BrickRPM design was decent, but in striving for compact design, there was excess trace coupling. It only showed up when I was heat testing it with 110v AC mains into it. In such a scenario the coupling was enough to cause the output signal to not be faithful. This was never struck in the real world by any of my customers. Their only complaint was that I didn't make more!

It was basically designed for people to replace the terrible MS circuit with something high performance in the prototype area, however over half of the stock went to industrial control applications! :-o

With respect Volvo 60-2 MAX IC performance, how high are you buggers spinning these poor things? I've tested to 8k RPM on a whiteblock with zero issues. 5k is all I can currently get out of my B234F with MAX but not due to the max, due to a slew of other issues on the car that I need to work through. Also used on a different pattern to 12500 RPM on a CBR600RR :-)

With respect to Bruce's comments, he first refers to the issues that guy had as being the fault of the max chip, and only later specifies that ADDING a shunt resistor FIXES the issue - and also that not all VR sensors need one at all. All of that is absolute crazy talk. The shunt resistor is basically REQUIRED or you'll have APPALLING high input impedance and susceptibility to noise. It can be tuned in value for problem applications, however in all the years I've been using them a value in the 1k to 5k has served me well when combined with 10k voltage clamp current limit resistors. The BrickRPM board doesn't have one to make sure it's tunable due to being an SMD design. The ancient docs suggest that you don't need the shunt, but encourage its use. I would now say the docs were a bit wrong by not mandating use of one.

I would suggest that if the MicroSquirt has issues at higher RPM on a Volvo 60-2 then there are other factors involved such as, but not limited to, circuit topology issues, PCB layout issues, wiring routing issues, etc. For example, in a boosted application with rising RPM comes rising cylinder pressure which causes ignition coil voltage to markedly increase prior to spark gap break down and discharge. And let's be honest, the vast majority of MS users on here are running one because they're boosting and/or boosting outside the stock capability. Or maybe MicroSquirt just doesn't have a shunt in place by default? Don't know and don't care. My stuff works :-)

Small update. I'm getting maximum 0.2v at the crank sensor when cranking. I think it's supposed to be about 0.4v based on the thread that was linked on the previous page. I guess I could try swapping the crank sensors once again, now that I've got better testing equipment.

I can't tell you if a 0.2v AC reading means bad sesnor or not. You could also do a resistance test across the two terminals. I also can't tell you what a good resistance would be. Open would obviously be no good.

A scope would reveal a lot more.

Do you have steady injector pulse? Noid light or a test light between injector ground and a good ground. Crank. Blink steadily?

I'm also curious to see what kind of reading you get on a meter st the powerstage input from EZK. In AC volts. I'm gonna go look for that 740 no start pdf a guy wrote years ago about this....

I had two problems. The first was that I used a bad power source for the ecu & ezk, so they were losing power during cranking. The second was that the only new part in the whole system wasn't working. I put the old ignition amplifier back on and hey presto.